Machine tools,particularly a device for bar feed mechanism and a bar feed mechanism

ABSTRACT

A device is employed in conjunction with a bar stock feed mechanism for a machine tool to support the bar stock intermediate its ends as the stock is rotated. The device utilizes a two part split collar whose parts are held closed by an over-center tension spring. The collar can be moved apart to a position in which the spring goes over-center and acts to hold the collar parts apart to allow the feed mechanism stock pusher to pass between the separated collar parts.

[ 1 Oct. 17,1972

United States Patent Mercer, Jr.

[56] References Cited UNITED STATES PATENTS MACHINE TOOLS, PARTICULARLYA DEVICE FOR BAR FEED MECHANISM AND A BAR FEED MECHANISM [72] Inventor:

3,606,807 9/l97l Auslm Cartwright Mercer, 'u 3,253,488 5/1966 Romano.....................82/38.l Guiseley, England [73l Assignee: MercerPneumatic Tools Limited Primary Exammer'-Gemld Foflenza AssistantExaminer-Frank E. Werner Filed: Dec. 14, 1970 21 Appl. No.: 97,908

Attorney-W0lf, Greenfield & Sacks [57] ABSTRACT A device is employed inconjunction with a bar stock [30] Foreign Application Priority DataApril 30, 1970 feed mechanism for a machine tool to support the barstock intermediate its ends as the stock is rotated. The

Great Britain.........

device utilizes a two part split collar whose parts are [52] US. R heldclosed by an ovebcemer tension spring The COL lar can be moved apart toa position in which the 8 R spring goes over-center and acts to hold thecollar parts apart to allow the feed mechanism stock pusher to passbetween the separated collar parts.

minnow n ma SHEET 1 UF 4 VE/ 9 AUSTIN CARTWRIGHT MERCER Jnr.

PATENTED 17 I973 3.698.269

SHEET 3 BF 4 )IVVE AUSTIN 'CARTWRIGHT MERCER Jnr.

ATTORNEYS PATENTEIJUCT 1 I912 3.698. 269

' SHEET '4 [IF 4 L/ENTOQ AUSTIN CARTWRIGHT MERCER Jnr.

V ATTORNEYS MACHINE TOOLS, PARTICULARLY A DEVICE FOR BAR FEED MECHANISMAND A BAR FEED MECHANISM This invention relates to machine tools and inparticular concerns a device for reducing the vibration and/ordeflection of bar stock in a bar stock feed mechanism for a machinetool, such as a capstan or turret lathe, in which the work is rotated.The invention also relates to bar feed mechanisms incorporating such adevice.

The modern trend in machine tools is for cutting speeds to be increasedand this means, in a case where the machinehas a bar stock feedmechanism, that the tendency is for the bar stock to be rotated faster.The increase in speed of rotation of the bar stock brings with it thedisadvantage that the vibration or whip deflection of the stock isincreased, the deflection being more pronounced as the cross section ofthe stock is decreased. To eliminate this, it has been shown to benecessary to provide some form of bearing support between the ends ofthe stock (in use one end of the stock is usually at the chuck of themachine tool, whilst the other end is usually engaged by the pusher ofthe bar stock feed mechanism). As the work is machined at the chuck, sothe pusher is moved to feed fresh stock to the chuck.

One known arrangement for supporting the stock is to provide a collar ofinternal diameter to suit the stock within the tube along which thestock is fed to the chuck. The disadvantage of this arrangement is thatwhen the pusher reaches the collar, it engages same and eventuallypushes it into the region of, and sometimes into engagement with, thechuck, and removal therefrom, when a fresh length of stock has to be putinto the mechanism, is difficult and time consuming as it must becarried out manually.

The present invention aims at providing a means of supporting bar stockbetween the ends thereof, as it is rotated in a bar stock feedmechanism, to reduce or eliminate, bar stock vibration and/ordeflection.

According to this invention there is provided a device for reducing oreliminating vibration and/or whip deflection of bar stock as it isrotated in a bar stock feed mechanism, including means defining a collarwhich is for disposition around the stock to support same, said meansbeing in two or more parts movable away from one another, said devicebeing adapted for locating on or adjacent a bar stock feed mechanism, sothat it can support a bar stock being rotated in the mechanism and sothat the parts of the means defining the collar can be moved away toallow the pusher to move between the displaced parts.

Preferably, there is holding means for holding said parts in thedisposition for supportingthe stock.

The said parts preferably comprise two arcuate yokes or shells of thesame radii, each with a replacea ble support pad or bush insert forengaging the stock. The shells, when they define the collar, arepreferably separated by a plane which lies at a slight incline, i.e.,approximately to the axis of the collar. The bush inserts may bereplaceable by inserts of differing sizes, depending upon the barstockto be supported.

The shells may be supported for pivoted or sliding movement away fromand towards each other, and the holding means may be a tension springmeans or a pneumatic or hydraulic cylinder means. In either case theholding means may be such as to have an over center position so thatwhen the said shells are furthest apart the holding means acts tomaintain such parts apart.

In another arrangement, the holding means is in the form of a stop foreach of said shells to prevent said shell from moving away from theother shell, said stop being movable to allow the said shell to moveaway from the other shell, and including loading means acting to moveeach of said shells apart.

The invention also provides a bar stock feed mechanism with one or moredevices as aforesaid. The or each device may be fitted so that it iseither knocked open by the pusher, as a result of the sensing of thepositions of the pusher in relation to the device.

Embodiments of devices according to the invention will now be described,by way of example, with reference to the accompanying drawings, wherein;

FIG. 1 is a side view of a bar stock feed mechanism with a deviceaccording to a first embodiment operatively mountedrelative thereto;

FIG. 2 is a side view of a detail shown in FIG. 1, but to an enlargedscale;

FIG. 3 is a plan view of the device shown in FIG. 1 with the coverremoved, also to an enlarged scale;

FIG. 4 is a sectional view of the device of FIG. 1 and taken on the linelV-lV of FIG. 3;

FIG. 5 is a plan view of a device according to second embodiment of theinvention and FIG. 6 is also a plan view of the device shown in FIG. 4but showing only the spring loaded arms and the center line of thespring which loads such arms when in the two extreme positions.

Referring firstly to FIG. 1, a bar stock feed mechanism comprises a baseframe 10 carryinga feed tube 12 which is in two sections 12A and 12B.The section 128 can be pivoted about an axis parallel to the tube axisto enable the bar stock to be fed into section 12A from the left handend in FIG. 1, and when the stock has been so loaded, the section 12B isreturned to the position shown in FIG. 1 and is held clamped in suchposition during working on the stock, by manipulation of locking handle14 which actuates a locking mechanism. The section 12B contains a pusherwhich is nearly equal to the length of section 12B and its right handend is adapted to engage the rear of the bar stock. The stock extendsout of the right hand end of section 12A into the machine, such as alathe,on which the work is to be carried out.

The pusher is moved by a fluid pressure ram through an endless chain 16trained round sprockets such as sprocket 18 at the ends of the wholetube 12.

The device according to this embodiment is shown at 18 and is adapted tosupport the bar stock intermediate its end during rotation of suchstock. As the bar stock is used up, the pusher is moved to the right inFIG. 1, thus presenting fresh stock to the machine. However, when theend of the pusher reaches the device 18, the need for the device islargely removed because the pusher continues to support the rear of thestock. Moreover, to continue feeding the bar stock, the bar supportingend of the pusher must move past the location of the device 18 and intothe machine. Because of these considerations, the device is arranged tobe rendered inoperative when the pusher reaches a predeterminedposition.

Considering now FIG. 2, in conjunction with FIG. 4, the device includestwo upright spindles 20 journalled in a bearing block 22. Each spindlehas secured thereto, for rotation therewith, a cheek plate 24 which hasa substantially semi-circular cut out 26. The device is a symmetricalarrangement and the plates 24 can be positioned as shown in FIG. 4 inthe same plane in which the cut outs 26 together define a circularaperture concentric with the axis of rotation of the bar stock in thefeed mechanism, or they can be positioned as shown in FIG. 2 atapproximately 90 to the FIG. 4 position in which case they are movedapart and allow the pusher to move therebetween.

As shown in FIG. 2 only, attached to each cheek plate 24 is one half 28of a split bush, the bore of which forms the bearing surface for the barstock during rotation thereof. These bush halves 28 are interchangeablefor other halves 28 of different bore sizes to suit the bar stock beingmachined, and are preferably constructed from some material which isused for bearing liners, such as bronze or certain alloys. The bushespreferably house a split plane which is at a slight inclination i.e.,approximately to the axis of the bush as this reduces chatter betweenthe joint of the bush halves and the rotating stock.

At the top end of each spindle there is a setting handle 30 with a handknob 32 and by means of these handles 30 the cheek plates 24 are movedto the bar stock-supporting position.

Considering now FIG. 3, in detail, each handle 30 has a lug 34 fromwhich a peg 36 extends downwardly. Rotatably carried on this peg 36 is aroller 38 which, as can be seen in FIG. 3 engages a notch stop 40 in onearm of a double armed lever 42 mounted for rotation about vertical axis44. As the arrangement is symmetrical there are two such levers 42.

The other arms of said levers 42 are urged together by a tension spring46 and also positioned between such arms is a fluid pressure operatedram device. This latter device comprises a cylinder 48 and two pistons50 respectively connected to said arms.

The supply of fluid under pressure, in this case preferably air, iscontrolled by a valve (not shown) which is in its turn controlled by theoperation of a sensing switch shown at 52 in FIG. 2. The switch ispositioned for actuation by a lug carried on the chain 16, at an instantwhen the pusher end is approaching the plates 24. We have found that asuitable position for actuation of switch 52 is when the pusher end isapproximately 1 inch from plates 26. This can be arranged easily byappropriate positioning of the actuating lug.

When the switch 52 is so actuated, and with the plates 24 in the closedposition, (handles 30 as shown in FIG. 3) pressure fluid supplied tocylinder 48 causes the piston 50 to be pushed outwardly and the levers42 to rock about their axes 44 so that notch stops 40 move out of thepaths of rollers 38, and tension springs 54, indicated by lines in FIG.3, pull the spindles 20 and cheek plates 24 round by approximately 90 inopposite directions so that the parts of the collar support of the barstock move apart to the FIG. 2 position in which the pusher can passthrough the device.

When reloading the bar feed mechanism the pusher will be withdrawn toits leftmost position in FIG. 1 the supply of pressure fluid to cylinder48 will be cut off and the halves 28 of the bush can be closed by movingthe spindles 20 by means of handles 30 back to the FIGS. 3 and 4position, against the action of springs 54.

It will be noticed also that the device has various oil bores 56 andchannels 58 to enable the bearings 60 for the spindles 20 and levers 42to be lubricated.

In this example the springs 54 are acting to open bush halves 28 withstops 40 preventing such opening until the desired time. In anotherexample, the springs could be acting to close the halves 28 with a fluidpressure device being actuated at the appropriate time to open thehalves against spring force. Alternatively, a fluid pressure operatedram could be arranged to be double acting to hold the halves closed uponbeing pressurized on one side and to open the halves upon beingpressurized on the other side. In yet another form there may be nosprings and only a single acting cylinder which is pressurized to movethe halves clear of holding catches at the appropriate instant in thecycle.

In another embodiment, the pivot axis of the halves may be remote fromthe halves so that such halves swing in an arcuate path of larger radiusof curvature. This could provide an arrangement which might be easier todesign from a mechanical engineering point of view.

From the above it will be appreciated that this invention may take manystructural forms. Indeed, instead of fluid pressure operated devices,solenoids could be used.

FIGS. 4 and 5 shown an embodiment wherein no fluid pressure operatedrams or solenoids are used.

Referring to FIGS. 5 and 6 the end of a section of feed tube of a barstock mechanism is indicated at and the device according to thisembodiment of the invention is mounted on the end of this tube section100. The device comprises a pair of mounting plates between which extenda pair of pivot pins 140, 160, which pins in plan view respectively lieon each side of the axis of tube section 100 and are vertical. Mountedon each of the pins 140, 160 is a pivotal assembly comprising a yoke orplate 180 with a semicircular cut-out 200 on one side thereof, the plate200 being secured to the pin or by a suitable screw 240. In FIG. 5, theplates are shown in the open position i.e., the position in which thesemi-circular cut-outs 200 are displaced furthest from one another.

In the closed position, the plates 180 are in alignment and the twocut-outs 200 co-operate to define a circular aperture in which the barstock is located in use.

FIG. 6 shows the means whereby the assemblies are held in one or otherof said closed and open positions. Each assembly is provided with springloading arm 260 and a tension spring 280 is connected to each of saidarms 260 tending to pull same together. The arms 260 are so located inrelation to the plates 180 that in the closed position the spring 280acts to maintain the plates in such position, whereas in the openposition the arms 260 go over-center and the spring loading then becomessuch as to maintain the plates 200 in the open position.

In an actual bar feed mechanism, a further length of feed tube sectionconnected to the machine tool would be located to the top side of thedevice as shown in FIG. 5 and indeed the Figure also shows the cone 300of the pusher in the position which it occupies as it passes through thedevice and between the plates 200.

In operation of the embodiment described, with reference to FIGS. and 6,the pusher is moved to a position furthest from the machine chuck andthe plates 200, after the bar stock has been loaded into the bar feedmechanism, are pivoted into the closed position around the bar stock,the radius of the arcuate cutouts 200 being selected to suit the size ofbar stock in the feed mechanism. In this position, when the stock isrotated, the plates 180, by cut-outs 200 serve to reduce or eliminatevibration and/or whip deflection of the bar stock. The plates 180 remainin the closed position until pusher cone 300 engages such plates andforces them to spring to the open position, by virtue of the pusher cone300 being pushed through the device by the pusher. With the device inthe open position the pusher can be pushed completely therethrough andtherefore the maximum possible of the bar stock is utilized.

The cut-outs 200 are lined with replaceable pads or bush inserts of anysuitable size and material, depending upon the size and finish of thebar stock to be supported thereby. Examples of suitable material for thebush inserts are bronze, nylon and hardened steel. These materials canalso be used for the FlGS.l-4 embodiment for shells 28. When it isdesired to change the bar stock size, the bush inserts are removed andthe bush inserts of the required size are inserted to give appropriateclearance between same and the bar stock.

In each of the described embodiments, although the means defining thesupport aperture for the bar stock comprises two parts i.e., two shells28 and two plates 180, the means may be made up of more than two partsand instead of the parts being pivotally mounted as shown they may bemounted for reciprocatory motion. Also the pivot assemblies may beprovided with intermeshing gear segments to ensure the simultaneouspivoting of the assemblies.

The devices, because they have circular support apertures, can be usedfor holding bar stock of circular, square or polygonal cross-section.

One of the main advantages of the devices described is that they openautomatically to allow the pusher to pass therethrough and they can bevery easily reset when the bar stock feed mechanism is re-loaded.

The benefit gained from this advantage is that the operator timerequired to set up the bar stock feed mechanism is minimal and is muchreduced in comparison with the known methods, wherein other means areused to support the bar stock.

The devices may also be adapted for automatic closing when a freshlength of bar stock is inserted into the feed mechanism.

In the case of an exceptionally long bar feed mechanism then two or moredevices according to the 0 es can be swun o a frst os'tion where th i0es form a collar dapte to e disposed around and support the stock andcan both be swung to a second position where the yokes are spaced apartto allow the bar stock feed mechanism pusher to pass between the yokes,and

spring means secured to said yokes, said spring means being disposed onone side of the center line joining the pair of parallel axes when theyokes are in the first position and said spring means being moved overthe center line when the yokes are moved to the second position wherebythe spring means acts to maintain the yokes in either positlon.

2. The device according to claim 1, further comprising replaceable bushinserts secured to the yokes, the bush inserts engaging the bar stock toprovide bearing surfaces when the yokes are in the first position.

3. A device for use with a bar stock feed mechanism of the type having abar stock feed tube and a pusher for pushing bar stock along the insideof the feed tube in the direction of the length of the stock toward amachine tool, the device acting to reduce or eliminate vibration andwhip deflection of the bar stock as it is rotated, the device comprisinga pair of arcuate yokes,

means supporting said yokes for pivotal movement about a pair ofparallel axes whereby both said yokes can be swung together to a firstposition where the yokes form a collar around the stock and can both beswung to a second position where the yokes are spaced apart to permitthe pusher to pass betweenthe yokes,

replaceable bush inserts secured to the yokes, the

bush inserts providing bearing surfaces for the bar stock when the yokesare in the first position, and spring means extending between andsecured to said yokes, said spring means being disposed on one side ofthe center line joining the pair of parallel axes when the yokes are inthe first position and said spring means being moved to the other sideof the center line when the yokes are moved to the second positionwhereby the spring means act to maintain the yokes in either position.

1. A device for reducing or eliminating vibration and whip deflection ofbar stock rotated in a bar stock feed mechanism, the device comprising apair of arcuate yokes means supporting said yokes for pivotal movementabout a pair of parallel axes whereby both said yokes can be swung to afirst position where the yokes form a collar adapted to be disposedaround and support the stock and can both be swung to a second positionwhere the yokes are spaced apart to allow the bar stock feed mechanismpusher to pass between the yokes, and spring means secured to saidyokes, said spring means being disposed on one side of the center linejoining the pair of parallel axes when the yokes are in the firstposition and said spring means being moved over the center line when theyokes are moved to the second position whereby the spring means acts tomaintain the yokes in either position.
 2. The device according to claim1, further comprising replaceable bush inserts secured to the yokes, thebush inserts engaging the bar stock to provide bearing surfaces when theyokes are in the first position.
 3. A device for use with a bar stockfeed mechanism of the type having a bar stock feed tube and a pusher forpushing bar stock along the inside of the feed tube in the direction ofthe length of the stock toward a machine tool, the device acting toreduce or eliminate vibration and whip deflection of the bar stock as itis rotated, the device comprising a pair of arcuate yokes, meanssupporting said yokes for pivotal movement about a pair of parallel axeswhereby both said yokes can be swung together to a first position wherethe yokes form a collar around the stock and can both be swung to asecond position where the yokes are spaced apart to permit the pusher topass between the yokes, replaceable bush inserts secured to the yokes,the bush inserts providing bearing surfaces for the bar stock when theyokes are in the first position, and spring means extending between andsecured to said yokes, said spring means being disposed on one side ofthe center line joining the pair of parallel axes when the yokes are inthe first position and said spring means being moved to the other sideof the center line when the yokes are moved to the second positionwhereby the spring means act to maintain the yokes in either position.